Method and Apparatus for Controlling A Plurality of Motors

ABSTRACT

Apparatus, having multiple motor modules, has an MCU module. Each motor module has an electronically controlled motor. The MCU module has an MCU and an interface for connecting to a bus from a CPU. In use the MCU module receives control signals from the CPU and in turn instructs a selected one of the motors to operate.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C. § 119(a) from Patent Application No. 0801450.8 filed in Great Britain on Jan. 28, 2008.

FIELD OF THE INVENTION

The present invention relates to a scheme for controlling a plurality of motors, particularly electronically controlled motors such as brushless DC motors and piezoelectric motor and in particular to apparatus of a passenger vehicle using such a scheme.

BACKGROUND OF THE INVENTION

Generally, the modern passenger vehicle has many electrically controller actuators. For example, actuators are used in the safety mirrors, in the seats and in vehicle air conditioning systems were they are used to control flaps or barriers used to control or redirect air flow within the vehicle, such as allowing more or less air to pass over a heat exchanger coil or to direct air to certain parts of the vehicle such as windscreen vents or feet vents. These flaps are moved by electric motors allowing control from a centralized control panel and, when fitted, from a remote control panel. They also allow automated control of the air conditioning system based on sensor feedback, etc.

Previously, these motors were generally PMDC brush motors. These types of motors are easy to control manually, have acceptable life and are relatively cheap. However, they are noisy either audibly or electrically or both. Noise is becoming a problem in the modern passenger vehicle. Audible noise has become very noticeable now that the passenger compartments are being effectively isolated from road and engine noise. Electrical noise is also important as the modern vehicle has not one but multiple computer systems and other electronic devices which are susceptible to electrical noise. For automated systems controlled by a computer, such as memory systems for the mirrors and seats and for automatically controlling the temperature within the passenger compartment, the motors are connected to the computer by a computer bus system such as a LIN Bus or CAN Bus. Electronically controller motors are more suited to this kind of system. One drawback to using electronically controlled motors is the cost of the electronics which may be more than the cost of the motor being controlled. In an air conditioning system, the changes occur slowly and thus most of the time the motors are idle. In the seat and mirror memory systems the system may be operated only when there is a change of driver.

The typical computer controlled system is shown in FIG. 1. The on board computer system, 10, which maybe a single computer or a number of computers linked together, is referred to as CPU. The plurality of motors, M1, M2, . . . Mn, are connected to the CPU via a LIN bus system. This requires each motor to be fully independent, having its own LIN bus driver, MCU, feedback sensor, power switch and identification. This is expensive in terms of electronic hardware which is used only occasionally.

SUMMARY OF THE INVENTION

The present invention aims to reduce the total cost of the electronics for a given system which uses a number of electronically controlled motors by sharing some of the electronic components (circuits) between the motors. This has the added benefit of increasing the reliability of the overall system by reducing the number of possible faults.

Accordingly, in one aspect thereof, the present invention provides apparatus comprising: an MCU module having an MCU and an interface for connecting to a primary bus from a CPU; and a plurality of motor modules, each motor module having an electronically controlled motor and an Identifier; wherein the motor modules are electrically connected to the MCU module, and the MCU module receives control signals from the CPU and in turn instructs a selected one of the motor modules to operate.

Preferably, the MCU module is connected to the motor modules by a bus.

Preferably, the bus carries high voltage AC signals for driving the selected motor.

Preferably, the MCU module further comprises a power switch circuit which provides power signals for operating the motors.

Preferably, the MCU determines which motor to select in response to a command from the CPU based on information provided by the Identifier.

Preferably, the motor module further comprises a feedback sensor for giving information to the MCU about a condition of the motor.

Preferably, the electronically controlled motors are piezoelectric motors.

Alternatively, the MCU module is connected to the motor modules by low voltage signal wires.

Accordingly, in a second aspect thereof, the present invention provides a method of controlling multiple electronically controlled motors, the method comprising the steps of: connecting a MCU to a bus from a CPU; connecting the MCU to the plurality of motors; using the MCU to select which motor to operate and in which direction based on the signals received by the MCU from the CPU.

Preferably, the method includes the steps of providing each of the motors as part of a motor module and connecting each motor to the MCU via an Identifier located in the motor module.

Preferably, the method includes the steps of providing a power switch circuit in each motor module to drive the respective motor.

Preferably, the method includes the steps of providing a power switch circuit in the MCU module and sharing the output from the power switch circuit with the motor modules.

According to a third aspect thereof, the present invention provides a method of controlling multiple electronically controlled motors, the method comprising the steps of using a single MCU to interface between the multiple motors and a CPU.

Preferably, the method includes the step of providing a single power switch circuit to selectively operate each of the motors and using the MCU to select which motor is to be operated based on instructions from the CPU.

Preferably, the method includes the steps of providing feedback sensors associated with each motor and passing signals from the feedback sensor to the MCU to determine when to deselect the selected motor.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a motor control scheme according to a conventional method;

FIG. 2 is a block diagram of a motor control scheme according to an embodiment of the present invention; and

FIG. 3 is a block diagram of a motor control scheme according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2 shows a block diagram of the first preferred embodiment of the present invention. The diagram shows the CPU 10, connected to a bus which we call primary bus 12. Primary bus 12 may be a LIN bus (Local Interconnection Network bus), a CAN bus (Controller Area Network bus) or a bus of another protocol. The primary bus connects the CPU to various components which are not shown and are generally known and do not form a part of this invention. Shown connected to the CPU 10 via the primary bus 12 is an MCU module 20. The MCU module 20 is connected to a plurality of motor modules 30, designated as M1, M2, . . . Mn, via a separate bus 22. Bus 22 is a low voltage signal bus carrying only low voltage signals for controlling the motor modules 30.

The MCU module 20 has an MCU 21 and a primary bus driver 23. The primary bus driver 23 enables the MCU 21 to send and receive signals over the primary bus 12. The motor modules 30 comprise an electronically controlled motor 31, power switch 24, an Identifier 32 for communication with the MCU and optionally, a feedback sensor or circuit 33, such as a position sensor. The bus 22 could be a dedicated hard wired bus if the number of motor modules 30 is small, otherwise a dedicated computer bus is preferred.

Thus, in this simple embodiment, a single MCU is share by all of the motor modules of the system or apparatus greatly reducing the total cost of the system. Also, only one primary bus driver is required, although a bus driver for exchanging signals with the MCU is required.

In the embodiment of FIG. 3, the MCU module 20 also has the power switch circuit 24. Thus the motor modules 30 have only the motor 31, the Identifier 32 and the optional feedback sensor 33. In this embodiment, the local bus 22 carries both the low voltage control signals as well as the power signal lines. For a stepper motor, a brushless DC motor and of a piezoelectric motor, etc., these power lines would carry high voltage pulses which are required to operate the motor.

In this second embodiment, the motor modules 30 share a common MCU 21, power switches 24 (the power driver circuit) and the primary bus driver 23, thus further reducing the total cost of the system or apparatus.

These embodiments have particular application where the electronically controlled motors are piezoelectric motors. In this scenario, the MCU module has the piezoelectric driver circuit and each motor module simply connects the motor to the driver signals sent out by the MCU module when that motor is selected to be activated. Selection is achieved by way of the Identifier. The driver signals are high voltage AC signals but the current level is relatively low compared to other types of DC motors. However, the arrangement can be used for other types of electronically controlled motors especially if the motors are physically located close by so that the bus 22 is short.

Thus it can be seen that the preferred embodiments of this invention provided a reduced cost of electronic components by sharing a number of these components between motors.

In the description and claims of the present application, each of the verbs “comprise”, “include” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items.

Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.

For example, while the invention has been described with reference to an air conditioning system for a passenger vehicle, it could be applied to other multiple motor systems found within a vehicle, such as the seat and mirror control and memory systems. Indeed, the invention could be applied to multi-motor systems of non-automotive applications.

Definitions of some of the abbreviations used in this description are:

CPU—Central Processing Unit MCU—Micro Controller Unit

LIN bus—Local Interconnection Network CAN bus—Controller Area Network

The term CPU or Central Processing Unit, can be used to refer to the processing chip within a computer or it may refer to the unit doing the data or signal processing and includes a computer, a series of computers and a central data processing processor. The computer system of the modern vehicle may have a number of computers working together in a distributed computer network and any of these computers, or all of the computers collectively may be referred to as the CPU.

LIN bus and CAN bus are two well known examples of primary bus protocols used in vehicle computer systems. 

1. Apparatus comprising: an MCU module having an MCU and an interface for connecting to a bus from a CPU; and a plurality of motor modules, each motor module having an electronically controlled motor and an Identifier; wherein the motor modules are electrically connected to the MCU module, and the MCU module receives control signals from the CPU and in turn instructs a selected one of the motor modules to operate.
 2. The apparatus of claim 1, wherein the MCU module is connected to the motor modules by a bus.
 3. Apparatus according to claim 2, wherein the bus carries high voltage AC signals for driving the selected motor.
 4. The apparatus of claim 1, wherein the MCU module further comprises a power switch circuit which provides power signals for operating the motors.
 5. The apparatus of claim 1, wherein the MCU determines which motor to select in response to a command from the CPU based on information provided by the Identifier.
 6. The apparatus of claim 1, wherein the motor module further comprises a feedback sensor for giving information to the MCU about a condition of the motor.
 7. The apparatus of claim 1, wherein the electronically controlled motors are piezoelectric motors.
 8. The apparatus of claim 1, wherein the MCU module is connected to the motor modules by low voltage signal wires.
 9. A method of controlling multiple electronically controlled motors, the method comprising the steps of: connecting a MCU to a bus from a CPU; connecting the MCU to the plurality of motors; using the MCU to select which motor to operate and in which direction based on the signals received by the MCU from the CPU.
 10. The method of claim 9, including the steps of providing each of the motors as part of a motor module and connecting each motor to the MCU via an Identifier located in the motor module.
 11. The method of claim 9, including the steps of providing a power switch circuit in each motor module to drive the respective motor.
 12. The method of claim 9, including the steps of providing a power switch circuit in the MCU module and sharing the output from the power switch circuit with the motor modules.
 13. A method of controlling multiple electronically controlled motors, the method comprising the steps of: using a single MCU to interface between the multiple motors and a CPU.
 14. The method of claim 13, including the step of providing a single power switch circuit to selectively operate each of the motors and using the MCU to select which motor is to be operated based on instructions from the CPU.
 15. The method of claim 13, including the steps of providing feedback sensors associated with each motor and passing signals from the feedback sensor to the MCU to determine when to deselect the selected motor. 